04 June 2015Arthropoda.ppt1 ARTHROPODS Phylum Arthropoda

04 June 2015Arthropoda.ppt2 Phylum Arthropoda Greek: arthro = jointed, + pod = foot Huge group, > 1,000,000 species. estimate: 1,000,000 spp. arthropods 1,190,000 spp. animals ~ 84% of all animal species are arthropods!!

04 June 2015Arthropoda.ppt3 Phylum Arthropoda Body plan Tube-in-tube, bilateral symmetry, protostomous, “split” coelom Marine, aquatic, terrestrial even Antarctica ! Cell and tissue organization Triploblastic, complex organs ~ 30,000 genes in genome, (same as for mammals)

04 June 2015Arthropoda.ppt4 Phylum Arthropoda Huge group, > 1,000,000 species. How can we explain the success of the arthropods?  Exoskeleton!

04 June 2015Arthropoda.ppt5 Phylum Arthropoda Exoskeleton of chitin and protein (= cuticle) structure: epicuticle (oily, waxy) exocuticle (chitin & protein) endocuticle (chitin only) epidermis secretes cuticle

04 June 2015Arthropoda.ppt6 Problems associated with exoskeleton. Problem 1. MOVEMENT Solution: Joints in exoskeleton. arthro-, = joint -pod, = leg, foot Exocuticle absent from joints; may form hinges. Endocuticle alone allows flexibility.

04 June 2015Arthropoda.ppt7 Problems associated with exoskeleton. Problem 2. GROWTH Solution: Molting

04 June 2015Arthropoda.ppt8 Molting (1) Secretion of "molting fluid" to dissolve old endocuticle.

04 June 2015Arthropoda.ppt9 Molting (2) New cuticle formed under old exocuticle. Break out of old cuticle Old cuticle breaks at line of weakness

04 June 2015Arthropoda.ppt10 Molting (3) Inflate with water/air to increase size while skeleton soft, but soft skeleton & gravity limit size; arthropods are mostly small. Hardening of new exocuticle.

04 June 2015Arthropoda.ppt11 Growth stages Arthropod passes thru growth stages in life cycle. Some stop molting as adults (insects, most spiders) Some continue to molt (crayfish, tarantulas)

04 June 2015Arthropoda.ppt12 Problems associated with exoskeleton. Problem 3. SENSORY INPUT touch sensory setae connected to neurons smell & taste hollow sensory setae w/ chemosensitive nerve endings

04 June 2015Arthropoda.ppt13 Problems associated with exoskeleton. Problem 3. SENSORY INPUT vision clear cuticle over compound or simple eyes

04 June 2015Arthropoda.ppt14 Problems associated with exoskeleton. Problem 3. SENSORY INPUT hearing tympanum = endocuticle, vibrates like eardrum trichobothria (right  )

04 June 2015Arthropoda.ppt15 Benefits of Exoskeleton: to individuals: Support Locomotion lever system walk, swim, fly Mechanical protection (armor) Retards evaporation (in air) and/or osmosis (in water) water balance.

04 June 2015Arthropoda.ppt16 Benefits of Exoskeleton: to the phylum: Reduction of coelom & segmentation Abandoned hydrostatic system of annelid-like ancestor; Coelom reduced to pericardial cavity Segments fused = Tagmosis Specialization of body regions (= tagmata) Specialization of appendages

04 June 2015Arthropoda.ppt17 Tagmosis Head (~ 4-6 segments)  feeding, sensation Head appendages mandibles, maxillae, maxillipeds, chelicerae antennae

04 June 2015Arthropoda.ppt18 Tagmosis Thorax (~ 3-6 segments) locomotion, grasping. Thoracic appendages walking legs, wings chelipeds

04 June 2015Arthropoda.ppt19 Tagmosis Abdomen (~ segments) respiration, reproduction, etc. Abdominal appendages abdominal gills (aquatic insect larvae) swimmerets (crayfish) filtering legs (barnacles) gonopods (crayfish, etc.) spinnerets (spiders)

04 June 2015Arthropoda.ppt20 Tagmosis Number of segments/legs in each tagma varies by subphylum, class. –Cephalothorax of 6 segments in Chelicerata 1 pr. chelicerae 1 pr. pedipalps 4 pr. walking legs –Cephalothorax of 13 segments in Crustacea (shrimps) 2 pr. antennae 1 pr. mandibles 2 pr. maxillae 3 pr. maxillipeds 5 pr. walking legs (1 st pair modified as chelipeds)

04 June 2015Arthropoda.ppt21 Phylum Arthropoda Ways the needs of cells are met Food—extremely diverse Herbivores, predators, detritivores, parasites, filter feeders,... O 2 and CO 2 exchange Gills—usu. modified legs, Book lungs, Tracheal systems Waste removal Diffusion from gills, Malphigian tubules

04 June 2015Arthropoda.ppt22 Other arthropod characters Open circulatory system Dorsal heart pumps hemolymph over brain Hemolymph moves through hemocoel back toward heart Ostia (holes) in sides of heart let hemolymph in to go around again.

Phylum Arthropoda Special concerns of a multicellular animal Circulation: Open circulatory system, (analogous to that in Mollusca) Dorsal aorta Hemocoel Pores (ostia) valved Text fig June 2015Arthropoda.ppt23

04 June 2015Arthropoda.ppt24 Other arthropod characters Respiratory systems Gills in aquatic/marine arthropods Book lungs (modified gills) in spiders & scorpions Tracheal systems in most terrestrial arthropods

04 June 2015Arthropoda.ppt25 Other arthropod characters Nervous system resembles that of annelid Dorsal brain with nerves around esophagus Paired ventral nerve cords Segmental ganglia Often fused into 1-2 ganglia in each tagma

04 June 2015Arthropoda.ppt26 Phylum Arthropoda Special concerns of a multicellular animal Circulation: Open circulatory system, Coordination, Complex sensory organs, nervous system Structural support & Movement Exoskeleton & muscles Maintenance of homeostasis—water balance.

Phylum Arthropoda Reproduction Usually sexual, sexes separate Some parthenogenic (asexual) 04 June 2015Arthropoda.ppt27

04 June 2015Arthropoda.ppt28 Distinguishing Characters of Arthropoda Jointed exoskeleton Tagmosis Compound eyes

04 June 2015Arthropoda.ppt29 Classification of Arthropoda

04 June 2015Arthropoda.ppt30 Classification of Arthropoda Subphylum Trilobita Subphylum Chelicerata Subphylum Myriopoda Clade Pancrustacea  Subphylum Crustacea (paraphyletic)  Subphylum Hexapoda

04 June 2015Arthropoda.ppt31 Classification of Arthropoda Subphylum Trilobita  Class Trilobita Three-lobed head & body (left, middle, right) Diverse in Paleozoic ~ MYA Extinct

04 June 2015Arthropoda.ppt32 Classification of Arthropoda Subphylum Chelicerata Cephalothorax Jaws are chelicerae Pedipalps 4 pr. Walking legs Abdomen

04 June 2015Arthropoda.ppt33 Classification of Arthropoda Subphylum Chelicerata  Class Merostomata Horseshoe crabs 4-5 living species

04 June 2015Arthropoda.ppt34 Classification of Arthropoda Subphylum Chelicerata  Class Arachnids  Lost compound eyes Spiders “Daddy-long-legs” vinegaroons mites & ticks more Scorpions

04 June 2015Arthropoda.ppt35 Classification of Arthropoda Subphylum Myriapoda Head & body  Class Centipedes 1 st legs are “fangs”

04 June 2015Arthropoda.ppt36 Classification of Arthropoda Subphylum Myriapoda Head & body  Class Millipedes Double segments (2 pr. legs per segment)

04 June 2015Arthropoda.ppt37 Classification of Arthropoda Clade Pancrustacea Subphylum Hexapoda Subphylum Crustacea 2 pr. Antennae (antennules, antennae) Cephalothorax 13 segments & appendage pairs Abdomen variable among Classes

04 June 2015Arthropoda.ppt38 Classification of Arthropoda Subphylum Crustacea  Class “crabs”  Class barnacles

04 June 2015Arthropoda.ppt39 Classification of Arthropoda Subphylum Hexapoda  Class Insects Head, thorax, abdomen 2 pr. Wings ~800,000 species, majority of all arthropods

04 June 2015Arthropoda.ppt40 Classification of Arthropoda Subphylum Hexapoda  Class Insects Incomplete metamorphosis Dragonflies Orthoptera Hemiptera, Homoptera Complete metamorphosis Coleoptera (beetles) Hymenoptera (wasps, ants, bees) Diptera (flies)

04 June 2015Arthropoda.ppt41 Why are Arthropods so successful? Exoskeleton  tagmosis  evolution of flight  speciation  10 6 species of insects.

04 June 2015Arthropoda.ppt42 Why are Arthropods so successful? Exoskeleton  protection from water loss  early colonization of land  head start. Arthropods were diverse and widespread on land before vertebrates!